Re: [PATCH 09/18] cxl: Add helper function to retrieve ACPI handle of CXL root device

[Dave Jiang <dave.jiang@intel.com>]

On 2/9/23 7:10 AM, Jonathan Cameron wrote:
> On Mon, 06 Feb 2023 13:50:42 -0700
> Dave Jiang <dave.jiang@intel.com> wrote:
> 
>> Provide a helper to find the ACPI0017 device in order to issue the _DSM.
>> The helper will take the 'struct device' from a cxl_port and iterate until
>> the root device is reached. The ACPI handle will be returned from the root
>> device.
>>
>> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
>> ---
>>   drivers/cxl/core/acpi.c |   30 ++++++++++++++++++++++++++++++
>>   drivers/cxl/cxl.h       |    1 +
>>   2 files changed, 31 insertions(+)
>>
>> diff --git a/drivers/cxl/core/acpi.c b/drivers/cxl/core/acpi.c
>> index 86dc6c9c1f24..05fcd4751619 100644
>> --- a/drivers/cxl/core/acpi.c
>> +++ b/drivers/cxl/core/acpi.c
>> @@ -5,6 +5,7 @@
>>   #include <linux/kernel.h>
>>   #include <linux/acpi.h>
>>   #include <linux/pci.h>
>> +#include <linux/platform_device.h>
>>   #include <asm/div64.h>
>>   #include "cxlpci.h"
>>   #include "cxl.h"
>> @@ -13,6 +14,35 @@ const guid_t acpi_cxl_qtg_id_guid =
>>   	GUID_INIT(0xF365F9A6, 0xA7DE, 0x4071,
>>   		  0xA6, 0x6A, 0xB4, 0x0C, 0x0B, 0x4F, 0x8E, 0x52);
>>   
>> +/**
>> + * cxl_acpi_get_root_acpi_handle - get the ACPI handle of the CXL root device
>> + * @dev: 'struct device' to start searching from. Should be from cxl_port->dev.
>> + * Looks for the ACPI0017 device and return the ACPI handle
>> + **/
> 
> Inconsistent comment style.

ok
> 
>> +acpi_handle cxl_acpi_get_rootdev_handle(struct device *dev)
>> +{
>> +	struct device *itr = dev, *root_dev;
> 
> Not nice for readability to have an assignment in a list of definitions
> all on the same line.

ok
> 
>> +	acpi_handle handle;
>> +
>> +	if (!dev)
>> +		return ERR_PTR(-EINVAL);
>> +
>> +	while (itr->parent) {
>> +		root_dev = itr;
>> +		itr = itr->parent;
>> +	}
>> +
>> +	if (!dev_is_platform(root_dev))
>> +		return ERR_PTR(-ENODEV);
>> +
>> +	handle = ACPI_HANDLE(root_dev);
>> +	if (!handle)
>> +		return ERR_PTR(-ENODEV);
>> +
>> +	return handle;
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_acpi_get_rootdev_handle, CXL);
>> +
>>   /**
>>    * cxl_acpi_evaluate_qtg_dsm - Retrieve QTG ids via ACPI _DSM
>>    * @handle: ACPI handle
>> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
>> index e70df07f9b4b..ac6ea550ab0a 100644
>> --- a/drivers/cxl/cxl.h
>> +++ b/drivers/cxl/cxl.h
>> @@ -733,6 +733,7 @@ struct qtg_dsm_output {
>>   
>>   struct qtg_dsm_output *cxl_acpi_evaluate_qtg_dsm(acpi_handle handle,
>>   						 struct qtg_dsm_input *input);
>> +acpi_handle cxl_acpi_get_rootdev_handle(struct device *dev);
>>   
>>   /*
>>    * Unit test builds overrides this to __weak, find the 'strong' version
>>
>>
>